The Strand Lane 'Roman Bath' is a brick-built cistern or tank, measuring about 1.9m by 4.75m at its longest point, with one square and one rounded end, and about 1.4m deep. It sits in a rectangular vaulted chamber about 3.8m wide by 7m long and 3.2m high, besides which runs a narrow entrance hall of about 1.7m by 9.3m, the end of which projects further east (towards Surrey Street) than the main bath chamber. Since the mid-nineteenth century it has enjoyed minor celebrity status as a London curiosity, thanks mainly to the puzzle of its true origins (Roman or later?), and its brief appearance in Charles Dickens's David Copperfield. It is not in fact a Roman relic, but its real history, from the early seventeenth century up until its acquisition by the National Trust in 1948, is a complicated and interesting one even so, embracing Stuart court pageantry and Georgian cold bathing as well as romantic fantasies of the Roman past, London antiquarianism, and the cultural politics of the parish of St Clement Danes.

Recent research by Professor Michael Trapp of King's College London, assisted by Dr Kevin Hayward of Pre-Construct Archaeology, has established that it was originally built not as a bath at all, but as the feeder cistern for a sumptuous grotto-fountain built in the gardens of the old, pre-Chambers Somerset House for James I's Queen, Anne of Denmark, in 1612. When the fountain was demolished (probably as early as the 1630s), the 'old water-house' (as it is referred to in early eighteenth-century documents) fell into disuse, and remained in this state at least into the mid-1720s.

The first definite sign of its conversion into a bathing facility comes in the form of a newspaper advertisement of November 1776, announcing that 'the Cold Bath, at No. 33, Surry-Street, in the Strand, is now open'. Two years later, the bath's proprietor, Mr James Smith of 33 Surrey Street, could announce that the Baths 'are now much enlarged', with separate entrances for ladies in Surrey Street and gentlemen in Strand Lane, and when his property was advertised for sale after his death in 1782, it included not one but two 'excellent and convenient well-accustomed Cold-Baths and Dressing-Rooms' in the back-house to No. 33.

It was James Smith, therefore, who seems to have constructed the second cold bath, subsequently (romantically but erroneously) connected with Queen Elizabeth's favourite the Earl of Essex. Though now covered over and only rarely accessible, the basic structure of this second bath still survives under the floor of King's College's Norfolk Building (the former Norfolk Hotel, once patronized at different times by Joseph Conrad and the agents of the Special Operations Executive French Section). But there are other, more visible traces of the old two-bath arrangement as well. Both the marble slabs stacked at the north end of the 'Roman' bath and the blue and white Dutch tiles on the walls of the entrance corridor originally decorated the 'Essex' bath, and were transferred from it when it was covered over by an extension to the Norfolk Hotel in 1893. The blocked doorway to the right of the corridor once led through to the second bath, while two other doorways, whose traces are just visible at the north end of the corridor and in the north wall of the bath chamber, once connected both baths to the back spaces of No. 33 Surrey Street.

The two-bath complex operated for the last two decades of the eighteenth century and through all but the last seven years of the nineteenth, over which period it came to be leased and managed separately from No. 33 Surrey Street, though with rights of access to the water supply reserved for the owner of the house. Lessees and mangers of the establishment lived not in the still surviving building, but in the original No. 5 Strand Lane, which stood over the 'Essex' Bath until demolished in 1893. At some time before 1841, bathing came to be confined to the better-appointed 'Essex' Bath only, with the 'Roman' bath reserved for drawing water and antiquarian contemplation.

Up until at least 1827, the establishment was only ever referred to as 'the cold bath' (whether at 33 Surrey Street or Strand Lane). The first reference to it as a Roman relic comes in a trade directory for 1838, when it was under the management of one Charles Scott. Since Scott only took over the management of the bath in the previous year, this is the likely time for the attachment of the Roman label, and the likely motive would seem to have been to try to drum up custom for an establishment that had lost its earlier attraction for a discriminating clientèle. But what may have begun as an advertising ploy was soon converted into a serious historical claim by being endorsed first by the account of the bath in Vol. II of Charles Knight's London, published in 1842, and then soon after by the inclusion of a reference to it in Chs 35 and 36 of Charles Dickens's David Copperfield, published in 1849-50. An antiquarian tug-of-war between believers and sceptics arose which was to last until just after the Second World War.

In 1893 the complex was bought by the proprietor of a New Oxford Street drapery business, Henry Glave. Though he seems initially to have wanted to maintain both baths, Glave very rapidly accepted an offer from the owner of the Norfolk Hotel to buy No. 5 Strand Lane and the 'Essex' bath, so as to allow him to extend his premises. It was at this point, just before the covering over of the 'Essex' bath, that Glave had its marble cladding, and the Dutch tiles on the walls, stripped off and transferred to the 'Roman' bath, along with some marble busts and columns that had also been part of the decoration. Glave, along with his daughters Blanche and Florence, and subsequently his son Nolan, then ran the surviving bath for several decades, principally as a visitor attraction, but with subscriptions also offered for active bathing. The venture did not prove hugely successful, and by the period of the First World War the bath was only opened sporadically, usually to raise money for charity.

Eventually, it was put on sale again, with some threat that it might be demolished if a suitable buyer could not be found. Its saviour, in 1922 for the sum of £500, was the Rector of St Clement Danes, the Reverend William Pennington-Bickford. Firmly convinced of the bath's Roman origins, Pennington-Bickford had all of the Glaves' (clearly unRoman) decoration stripped off again, so as to get back to the 'genuine' fabric. He also planned an ambitious programme of excavation, to discover the rest of the Roman river-side villa he suspected the bath once belonged to, and if possible to restore it. The plan got as far as an appeal for funds, and a gorgeous sub-Alma Tadema project drawing by the artist Fortunino Matania, but foundered for lack of public interest.

Nothing more had been done by the outbreak of war in 1939. Both the Reverend Pennington-Bickford and his wife died following the bombing and burning out of St Clements in 1941, he it was said of a broken heart at the destruction of his life's project, and she from her inability to live without him. The combination of wartime conditions and problems over Mrs Pennington-Bickford's will meant that the question of the future of the bath could only be addressed at the end of hostilities. It was offered to the National Trust, who commissioned an enquiry into its history and origins from the London County Council Architect's Office. This concluded that although the bath was very unlikely to be Roman – a connection with Arundel House was suggested instead – it was nevertheless of enough historical interest for it to be worth the Trust's while to take it on. The Trust agreed, but on condition that the money requested by Mrs Pennington-Bickford's executors, and the responsibility for day-to-day maintenance, be provided for by someone else. The money was put up by a generous local businessman, Montague Meyer, management responsibilities were accepted by the LCC, and the bath became the Trust's property in 1948.